JPH0767694B2 - Method for producing fiber-reinforced thermoplastic resin molding material - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for producing a fiber-reinforced thermoplastic resin molding material used for heat and pressure molding. Molded articles using the fiber-reinforced thermoplastic resin molding material according to the present invention,
Widely used in industrial parts such as automobiles.

[Prior Art] Recently, parts manufactured by press molding of metal, such as automobile front-end retainers, seat shells, lamp housings, battery trays, bumper beams, etc., have become press-molded products of fiber-reinforced thermoplastic resin. Tend to be replaced. Fiber-reinforced thermoplastic resin is characterized by inserting a heated sheet-shaped molding material into a molding die heated at room temperature or in a short time, and compression-molding it in a short time to partially change the wall thickness of the product, boss or rib. It is possible to manufacture a complicated molded product to which, etc. are added, and the molded product has high mechanical strength and is lightweight.

The method for producing the fiber-reinforced thermoplastic resin sheet-shaped molding material can be classified into the following two methods.

Lamination method: Needling (Process of piercing multiple strand-like reinforcing fibers with needles and entwining them with each other)
The mat-shaped strand-reinforced fiber and thermoplastic resin are laminated and continuously inserted between the steel belts of a double-belt conveyor type continuous press, heated and pressed, and further cooled to form a sheet-shaped molding material. Method for manufacturing
48-80172, JP 52-40558, JP 55-
77525 gazette) and papermaking method: A papermaking technique is applied to produce a nonwoven material in which reinforcing fibers cut to a length of about 3 mm to 50 mm and a powdery thermoplastic resin are uniformly dispersed. This is a method of producing a sheet-shaped molding material by heating and pressurizing the material as a raw material and further cooling it (Japanese Patent Laid-Open Nos. 49-13403 and 49-14704).

It is important that these sheet-shaped molding materials flow in a complicated molded product without the separation of the reinforcing fibers from the thermoplastic resin and that the reinforcing fibers float on the surface of the molded product, which is important during heat and pressure molding. It is required to prevent the deterioration of the appearance due to.

In the case of sheet-like molding material manufactured by the laminating method,
Since the strand reinforcing fibers in the mat are restrained by the needling treatment, there arises a problem that the reinforcing fibers and the thermoplastic resin are easily separated when flowing in the molding die.

On the other hand, in the case of a sheet-shaped molding material manufactured by the papermaking method,
Since the discontinuous reinforcing fibers that are uniformly dispersed are present in the thermoplastic resin in a state in which they are less bound to each other, a homogeneous molded product can be obtained without causing the above problems. However, the non-woven material produced by the papermaking method has a property that it is extremely bulky because the reinforcing fibers are randomly oriented. The thickness of the non-woven material varies depending on the shape of the reinforcing fiber and the papermaking conditions, but it is about 10 times as thick as the sheet from which voids that are generally used in press molding of fiber-reinforced thermoplastic resin are removed. .

The sheet-shaped molding material is heated before the softening point or melting point of the thermoplastic resin constituting the matrix before molding,
At that time, since the binding force of the thermoplastic resin to the reinforcing fibers is weakened, the sheet expands due to the springback of the reinforcing fibers to return to the original state. This expansion starts from the surface of the sheet and gradually expands as heat reaches the central portion of the plate thickness, and along with this, an adiabatic air layer is formed in the sheet, so that the thermal conductivity decreases. As a result, the temperature rise of the thermoplastic resin at the center of the sheet thickness is obstructed, which lowers the fluidity during molding, and because the sheet surface is locally heated, the thermoplastic resin decomposes due to thermal decomposition. Then
The reinforcing fibers float, causing problems such as deterioration of the appearance of the molded product and reduction of strength.

As a heating method that does not increase the temperature difference between the surface of the sheet-shaped forming material and the plate thickness center part, it is possible to set the atmosphere temperature of the heating furnace low and heat it for a long time, but it is industrially possible. In this case, the molding cycle time becomes long, and the thermoplastic resin on the sheet surface may be thermally deteriorated in some cases, so it is difficult to take sufficient measures.

[Problems to be Solved by the Invention] An object of the present invention is to provide a method for producing a fiber-reinforced thermoplastic resin sheet-shaped molding material with high heating efficiency, which eliminates the above-mentioned drawbacks.

[Means for Solving the Problems] The present invention provides a fiber-reinforced thermoplastic resin molding material by heating, pressurizing, and further cooling a nonwoven material obtained by a paper-making technique, which contains reinforcing fibers and a thermoplastic resin as main components. In the method for producing, the reinforcing fibers in the non-woven material are characterized by comprising a reinforcing fiber bundle in which a plurality of single fibers are bundled, or a mixture of single fibers and the above-mentioned reinforcing fiber bundle. It is a method for producing a thermoplastic resin.

An example of the manufacturing process of the fiber-reinforced thermoplastic resin sheet-shaped molding material by the papermaking method is shown in FIG. Diameter 3 μmφ to 30
The reinforcing fiber 1 and the powdery thermoplastic resin 2 cut to a length of about 3 mm to 50 mm with μmφ are continuously charged into water in the dispersion tank 3. In the dispersion tank, stirring is performed in order to uniformly disperse the reinforcing fiber and the thermoplastic resin, and the dispersion liquid is supplied by the pump 4 to the head box 6 installed above the mesh belt conveyor 5. The inside of the wet box 7 installed under the head box is kept at a negative pressure to suck and dehydrate the dispersion liquid in the head box to continuously form the non-woven material 8 which is a composite of the reinforcing fiber and the thermoplastic resin. To manufacture. This non-woven material is dried by a ventilation type hot air dryer 9, then heated and pressed by a double belt conveyor type continuous press 10 and further cooled to form a sheet, which is finally heated and pressed. The fiber-reinforced thermoplastic resin sheet-shaped molding material 12 is manufactured by cutting with a cutter 11 into a shape according to the required size.

As the fiber-reinforced thermoplastic resin sheet-shaped molding material, in addition to the material in which the voids in the sheet are completely removed, a material having voids can be provided. Further, without using the double belt conveyor type continuous press, at the same time as drying the non-woven material in a hot air dryer, a part or all of the thermoplastic resin is heated above its softening point or melting point to obtain a thermoplastic resin. It is also possible to provide a sheet-shaped molding material in which voids are present, in which the reinforcing fibers are melted and cooled to bond the reinforcing fibers with the thermoplastic resin. The sheet-shaped forming material having the voids can be easily bent depending on the raw material blending and the heating and pressurizing conditions. Therefore, the product can be provided as a coil by reeling up.

Since such a sheet-shaped molding material leads to cost reduction by omitting steps and can provide air permeability in the thickness direction of the warm sheet, in addition to far-infrared heating which is conventionally used for heat and pressure molding. Even if a ventilation type heating device is used, heating can be performed efficiently in a short time.

Reinforcing fibers used in conventional papermaking methods are water-soluble polymers and lubricants for improving dispersibility in water, and silane coupling agents for improving adhesiveness with the thermoplastic resin forming the matrix. Has been surface treated.
Therefore, as a raw material for the fiber-reinforced thermoplastic resin sheet-shaped molding material, the reinforced fiber 1 and the powdery thermoplastic resin 2 as shown in FIG. 2 are uniformly dispersed, and a non-woven material having a very bulky property. Is obtained.

In the present invention, in order to increase the bulk density of the non-woven material produced by the papermaking method, in place of the conventionally used reinforcing fiber, a reinforcing fiber bundle obtained by bundling a plurality of single fibers as the reinforcing fiber is used? Alternatively, the reinforcing fibers of the single fiber and the reinforcing fiber bundle are mixed and used. The fibers in the reinforcing fiber bundle are
In addition to the silane coupling agent, it is strongly bound with a urethane-based or vinyl acetate-based binder for the purpose of not dispersing in water. When the reinforcing fiber and the reinforcing fiber bundle are mixed and used, a non-woven material as shown in FIG. 3 in which the reinforcing fiber 1, the reinforcing fiber bundle 13 and the powdery thermoplastic resin 3 are uniformly dispersed is obtained. .

The fiber-reinforced thermoplastic resin sheet-shaped molding material produced by using the nonwoven material having an increased bulk density as a raw material according to the present invention suppresses the springback of the reinforcing fiber during heating, so that the sheet expansion is reduced and the heating efficiency is improved. It is possible to improve and improve the fluidity at the time of molding and the appearance of the molded product by the uniform heating.

The effect of suppressing the expansion of the sheet by using the reinforcing fiber bundle changes depending on the ratio of the entire reinforcing fibers constituting the nonwoven material, but is improved by increasing the number of single fibers bundled in the reinforcing fiber bundle and the mixing ratio thereof. However, as the number of single fibers bundled in the reinforcing fiber bundle and the mixing ratio increase, the appearance of the molded product deteriorates due to surface exposure of the reinforcing fiber bundle.
To 30 μmφ and from 10 to 1000 single filaments of reinforcing fiber cut into lengths of 3 mm to 50 mm are used to fabricate non-woven materials at a mixing ratio according to the molding application. It is desirable to do.

The raw material thermoplastic resin used in the present invention is polyethylene, polypropylene, polystyrene, styrene-butadiene-acrylonitrile copolymer, styrene-acrylonitrile copolymer, polyvinyl chloride, polyvinylidene chloride, polyamide, polycarbonate, polyacetal,
Resins such as polyethylene terephthalate, polybutylene terephthalate, polyphenylene oxide, polysulfone, polyphenylene sulfide, etc., and also including mixtures of two or more of these, plasticizers, heat stabilizers, light stabilizers commonly used in these Agents, fillers, face wash, impact resistance agents, extenders, nucleating agents, processing aids, short glass fibers and the like can be added.

In the present invention, glass fibers, carbon fibers, metal fibers as well as inorganic fibers and organic fibers are used as the reinforcing fibers, and it is desirable that the shape is a diameter of 3 μmφ to 30 μmφ and a length cut to about 3 mm to 50 mm.

The fiber-reinforced thermoplastic resin sheet-shaped molding material obtained in the present invention exhibits excellent performance as a general material for heating and pressurizing, but even in pressure-pressure molding and the like, beneficial results are brought about by improving its heating characteristics. Be done.

[Examples] The present invention will be described in detail below with reference to Examples.

(Example 1) A glass fiber A having a diameter of 10 μmφ and a length of 25 mm treated with a water-soluble polymer as a reinforcing fiber, a lubricant, and a silane coupling agent, and a diameter of 10 μmφ treated with a silane coupling agent and a urethane binder, By using a glass fiber bundle B in which 67 glass fibers of 13 mm in length are bundled, 40% by weight of reinforcing fibers and 60% by weight of polypropylene resin are produced by a papermaking method.
A non-woven material having a composition of 4 and a basis weight of 4500 g / m ² was produced.

For polypropylene resin, spherical pellets with a diameter of 3 mmφ are crushed, and the crushed product is sieved to obtain 70 mesh (opening diameter).
A powder classified from 0.212 mm) to 10 mesh (opening diameter 1.7 mm) was used. Table 1 shows the mixing ratio of the glass fiber A and the glass fiber bundle B constituting the nonwoven material. Using these non-woven materials as raw materials, a 3.7 mm-thick fiber-reinforced thermoplastic resin sheet with voids removed by hot press molding was formed.

The hot press molding was carried out by preheating the non-woven material for 10 minutes at 210 ° C. under no load, then applying pressure at 20 kgf / cm ² for 5 minutes, cooling and solidifying to form a sheet. Further, in order to measure the temperature difference between the surface of the sheet and the central portion of the plate thickness during heating, a thermocouple was previously inserted into the surface and the central portion of the nonwoven material to form the sheet. These sheets were heated in a far-infrared heating furnace until the surface temperature of the sheets rose to 220 ° C., and the sheet thickness after heating and the temperature difference between the sheet surface and the center of the sheet thickness were measured.

The non-woven material produced by mixing the glass fibers A and the glass fiber bundles B is made of polypropylene with the glass fibers A in a single fiber state and the glass fiber bundles B in a bundled state as shown in FIG. It was uniformly dispersed together with the resin powder, and its bulk density increased as the mixing ratio of the glass fiber bundle B increased.

The result of the heating experiment of the sheet obtained in Example 1 is shown in FIG. Glass fiber A 40wt% and polypropylene resin powder 6
The sheet formed from a non-woven material composed of 0 wt% has a large spring back of the glass fiber A, so the sheet thickness after heating is about 12 mm and the initial thickness of 3.7 m.
It expanded to about 3.2 times m. Therefore, the thermal conductivity of the sheet was remarkably reduced, the temperature difference between the surface of the sheet and the central portion of the plate thickness was 55 ° C, and the temperature of the central portion of the plate thickness was 165 ° C, which was close to the melting point of the polypropylene resin. Further, it was confirmed that the polypropylene resin on the surface of the heating sheet was thermally deteriorated and the glass fiber floated. It is impossible for such a sheet to provide good fluidity and a molded product appearance required for molding a fiber reinforced thermoplastic resin.

It was confirmed that the mixing of the glass fiber bundle B improves the heating characteristics of the fiber-reinforced thermoplastic resin sheet. The effect of suppressing the sheet expansion was improved with an increase in the mixing ratio of the glass fiber bundle B. It was observed that the decrease in the sheet expansion reduces the temperature difference at the center of the sheet thickness on the sheet surface, and suppresses the thermal deterioration of the polypropylene resin on the surface of the heating sheet. However, due to the increase in the mixing ratio of the glass fiber bundle B, the exposure on the surface of the molded product becomes noticeable.
When a fiber reinforced thermoplastic resin sheet having a reinforcing fiber content of 40 wt% is used as a molding material, the glass fiber A is 20 wt% and the glass fiber bundle B is 20 wt, although it varies depending on the molding application.
%, And polypropylene resin of 60 wt% makes it possible to obtain good fluidity and appearance of a molded product in heat-press molding of a complicated shape.

(Example 2) The glass fiber A and the polypropylene resin used in Example 1,
Further, a glass fiber bundle C in which the same number of glass fibers as the glass fiber bundle B are used and the surface treatment is performed to vary the number of single fibers
(200 bundles) and glass fiber bundle D (500 bundles)
A non-woven material having a basis weight of 4500 g / m ² was produced by the papermaking method. The composition of the non-woven material is 20 wt% of glass fiber A.
%, Glass fiber bundle C or D was 20 wt%, and polypropylene resin was 60 wt%. Using these non-woven materials as raw materials, a fiber-reinforced thermoplastic resin sheet having a thickness of 3.7 mm was molded by hot press molding under the same molding conditions as in Example 1. Further, the sheet was heated in a far infrared heating furnace until the surface temperature of the sheet rose to 220 ° C., and the sheet thickness after heating and the temperature difference between the sheet surface and the center of the sheet thickness were measured.

The result of Example 2 is shown in FIG. 5 together with the result of the glass fiber B of Example 1.

It was confirmed that by increasing the number of single fibers bundled in the glass fiber bundle, the heating characteristics of the fiber-reinforced thermoplastic resin sheet were improved, and the fluidity in the heat and pressure molding was also improved.

[Effects of the Invention] According to the present invention, the heating characteristics of a fiber-reinforced thermoplastic resin sheet-shaped molding material made of a non-woven material, which is a composite of reinforced fibers and a thermoplastic resin by a papermaking method, are improved. The fiber-reinforced thermoplastic resin sheet-shaped molding material obtained in the present invention has improved heating efficiency because sheet expansion due to springback of reinforcing fibers is suppressed during heating during molding.
By uniformly heating the sheet, good fluidity is exhibited, and the appearance of the molded product is also improved.

[Brief description of drawings]

FIG. 1 is a schematic view showing an example of a manufacturing process of a fiber-reinforced thermoplastic resin sheet-shaped molding material by a papermaking method. FIG. 2 is a schematic view of a non-woven material used for manufacturing a conventional fiber-reinforced thermoplastic resin sheet-shaped molding material. FIG. 3 is a schematic view of a non-woven material used for producing the fiber-reinforced thermoplastic resin sheet-shaped molding material of the present invention. FIGS. 4 and 5 are diagrams showing the sheet expansion and the temperature difference between the sheet surface and the center of the plate thickness when the fiber reinforced thermoplastic resin sheet is heated. 1 ... Reinforcing fiber, 2 ... Thermoplastic resin powder, 3 ... Dispersion tank, 4 ... Pump, 5 ... Mesh belt conveyor,
6 ... Head box, 7 ... Wet box, 8 ...
… Nonwoven materials, 9 …… Hot air dryer, 10 …… Double belt conveyor continuous press, 11 …… Cutter, 12 …… Fiber reinforced thermoplastic resin sheet material, 13 …… Reinforced fiber bundle.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Hiroyuki Uchino 1618 Ida, Nakahara-ku, Kawasaki-shi, Kanagawa Inside the 1st Technical Research Laboratory, Nippon Steel Corporation (72) Kensuke Ohno, 1 Toho-cho, Yokkaichi-shi, Mie Mitsubishi Petrochemical Co., Ltd. Yokkaichi Research Institute (72) Inventor Takao Kimura 1 Toho-cho, Yokkaichi-shi, Mie Mitsubishi Petrochemical Co., Ltd. Yokkaichi Research Institute (56) Reference JP-A-1-318045 (JP, A) ) JP-A-1-299828 (JP, A) JP-A-63-135430 (JP, A) JP-A-63-219697 (JP, A) International publication 89/1075 (WO, A)

Claims (1)

[Claims] 1. A strength fiber and a thermoplastic resin as main components,
In a method for producing a fiber-reinforced thermoplastic resin molding material by heating, pressurizing and cooling a non-woven material obtained by a papermaking technique, the reinforcing fiber in the non-woven material is a reinforcing fiber obtained by bundling a plurality of single fibers. A method for producing a fiber-reinforced thermoplastic resin molding material, which comprises a bundle or a mixture of single fibers and the above-mentioned reinforcing fiber bundle.